Hydraulic machines



. 1966 G. w.- P. SCOTT ETAL 3,

HYDRAULIC MACHINES Filed Dec. 2, 1964 2 Sheets-Sheet IL NOV. 8, 1956 e.w. P. SCOTT ETAL 3,283,725

HYDRAULIC MACHINES 1 il l United States Patent 3,283,725 HYDRAULICMACHINES George William Pearson Scott, Bowbridge, Stroud, and

George Alan Montgomerie, Leamington, England, assignors to Serck R & DLimited, Birmingham, England Filed Dec. 2, 1964, Ser. No. 415,278 Claimspriority, application Great Britain, Dec. 10, 1963,

v 48,666/ 63 3 Claims. (Cl. 103162) This invention relates to hydraulicmachines of the kind comprising a housing, a rotatable shaft mounted inthe housing, a rotor drivingly connected to said shaft, said. rotorbeing formed with a plurality of passages, a pair of ports in one end ofthe housing arranged so that during rotation of the rotor said passagesare brought successively into communication with ports, a plurality ofpistons slideable respectively in the passages, and an inclined camsurface, at the end of the housing remote from the ports, against whichthe pistons bear so that rotary movement of the rotor is accompanied byaxial movement of the pistons.

It is an object of the invention to provide an hydraulic machine of thekind specified in a convenient form.

According to the invention, in an hydraulic machine of the kindspecified, each piston is hollow and is provided at its cam-engaging endwith a slipper of cup-shaped form, the interior of the pistoncommunicating with the interior of the slipper through a restricted boreand the slipper having and end face which is inclined to the axis of theslip-per at an angle substantially corresponding to the inclination ofthe cam surface.

Reference will now be made to the accompanying drawings in which FIGURE1 is a longitudinal section of one example of a motor according to theinvention and FIGURES 2, 3 and 4 are enlarged sections showing threedifferent forms of piston for the motor shown in FIG- URE 1.

As shown in FIGURE 1 the motor includes a housing in which a shaft 11 isrotatably mounted. Also rotatably supported by hydrostatic bearings inthe housing 10 is a rotor 12, which is drivingly connected to the shaft,by virtue of the non-circular section of its central passage 12a and thenon-circular section of the associated part 11a of the shaft.

Formed in the rotor 12 are a series of axially extending passages inwhich pistons 13 are reciprocably mounted. These pistons project fromone end of the rotor 12 and have slippers 14 bearing against an inclinedcam surface 15 formed on a cylindrical block secured to the housing 10.It will thus be seen that rotation of the rotor 12 causes the pistons 13to be reciprocated in their respective passages.

Formed in the port plate 16 which provides an end wall of the housing,are a pair of ports 17, 18 through which liquid enters and leaves themotor respectively. These ports are so disposed that the end of thepassages in the rotor are brought successively into communication withthe ports as the rotor is turned.

Referring now to FIGURE 2 the piston 13 shown therein has the slipper 14formed integrally thereon. As shown the piston is formed at variouspositions along its length with circumferential oil retaining grooves19. It will also be seen that the slipper 14 is of generally cup shapedform with its axis aligned with the axis of the piston 13. The end face14a of the slipper is, however, inclined to the common axis of thepiston and slipper at an angle corresponding to the inclination of thecam surface 15.

The interiors of the slipper 14 and. piston 13 are interconnected by afine bore 20.

3,283,725 Patented Nov. 8, 1966 Thus, in use, when high pressure liquidis supplied to port 17 the interiors of the slippers will fill withpressurized liquid and will form an hydrostatic bearing between theslippers 14 and the cam surface 15. The spacing of face 14a from thesurface 15 will regulate the rate at which liquid leaves the interior ofthe slipper and variation of flow through bore 20 will cause changes ofpressure within the slipper as is known in hydrostatic bearings. 7

Turning now to FIGURE 3 (in which all reference numerals have beenincreased by the piston 113 and the slipper 114 are formed separatelyand are sealingly joined together. The end of piston 113 is closed bywall 1130 in which bore is formed. Also formed in the end wall 113a is asubstantially hemispherical recess 11312. The periphery of the end ofthe piston is of somewhat reduced diameter and, in fact, may be offrusto-conical form as shown.

The slipper 114 is formed with a central hemispherical projection 114bwhich fits into the recess 113b, a large bore 113c being formed in thisprojection and communicating with the interior of the slipper 114. Theslipper also has a cylindrical skirt portion 114d surrounding thereduced. end of the piston. The end face 1140 of the slipper is inclinedas before.

The slipper 114 and piston 113 are joined together by means of a ring121 of rubber or other elastomeric material. This ring is formed bytreating the piston and slipper to form suitable keying surfaces,locating them together in the required relative position, injecting theraw elastomer into the space between the piston 113 and the skirtportion 114d and then curing the elastomer. Alternatively where theelastomer cannot be injected, a preformed ring of the raw elastomer maybe inserted in the space during assembly. In either case when theelastomer is cured it becomes firmly bonded to the metal surfaces andforms a flexible but fully liquid-tight joint.

This flexible joint enables the slipper 114 to move slightly relative tothe piston 113. Such movement is, however, restricted to turning of theslipper about the centre of the mating spherical surfaces. Thrust andjournal loads on the slippers are transmitted directly to the pistonwithout much effect on the ring 121. The movement of the slipper enablesit to follow any irregularities in the cam surface and to allow for thebending of the pistons that occurs under load without any undue loss ofpressure within the slippers.

Referring now to FIG. 4 (in which reference numerals have again beenincreased by 100) the piston 213 is formed with a convex part sphericalend 213a which fits against a complementary surface within the skirtportion 214d of slipper 214. The bore 220 is, in this case, formed inthe slipper 214. The piston 213 and the slipper 214 are again bondedtogether by a ring 221.

In this case the piston receives directly any thrust on the inclinedslipper face 214a, but journal loads are taken by the ring 221.

In the embodiments shown in FIGURES 3 and 4 the ring 121 or 221 cured insitu may be replaced by a ring already cured and bonded in positionusing any suitable adhesive. Moreover (although not shown) a flexiblemetal bellows may be employed to form the flexible and sealed connectionbetween the piston and the slipper. Once again the piston and theslipper would preferably be interengaged so that the bellows do not haveto transmit thrust and journal loads.

The invention may be applied in like manner to hydraulic pumps andcouplings.

Having thus described our invention what we claim as new and desire tosecure by Letters Patent is:

1. An hydraulic machine comprising the combination of a rigid housing, ashaft rotatable within the housing,

a rigid cam block rigidly secured within the housing and providing a camface extending in a plane inclined to the shaft axis, a rotor enclosedwithin the housing and drivingly coupled to the shaft, said rotor beingformed with a plurality of passages, a pair of ports in one end of thehousing arranged so that during rotation of the rotor the passagestherein are brought successively into communication with the ports, aplurality of pistons slidable respectively in the passages andprojecting from one end of the rotor towards the cam face, a pluralityof cup-shaped slippers mounted respectively on the pistons where theseproject from the rotor, each slipper including a skirt portionencircling the piston, a cupped end face remote from the skirt portionand inclined to the axis of the skirt portion at an angle equal to theinclination of the cam face to the shaft axis and a portion engageddirectly against the end of the associated piston, and a plurality ofelastomeric rings coupling the respective slippers to the pistons, eachring being sealingly bonded to the interior of the associated skirtportion and to the piston and each piston/ slipper combination having arestricted bore connecting the interior of the associated passage to theinterior of the slipper to form between each slipper and the cam face, ahydrostatic bearing.

References Cited by the Examiner UNITED STATES PATENTS 2,847,938 8/1958Gondek 103162 2,901,979 9/1959 Henrichsen 103-462 3,095,221 6/1963 Kaup287-21 3,120,816 2/1964 Firth et al 103162 3,221,564 12/1965 Raymond103162 X MARTIN P. SCHWADRON, Primary Examiner.

I. C. COHEN, Assistant Examiner.

1. AN HYDRAULIC MACHINE COMPRISING THE COMBINATION OF A RIGHT HOUSING, ASHAFT ROTATABLY WITHIN THE HOUSING A RIGID CAM BLOCK RIGIDLY SECUREDWITHIN THE HOUSING AND PROVIDING A CAM FACE EXTENDING IN A PLANEINCLINED TTO THE SHAFT AXIS, A ROTOR ENCLOSURE WITHIN THE HOUSING ANDDRIVINGLY COUPLED TO THE SHAFT, SAID ROTOR BEING FORMED WITH A PLURALITYOF PASSAGES, A PAIR OF PORTS IN ONE END OF THE HOUSING ARRANGED SO THATDURING ROTATION OF THE ROTOR THE PASSAGES THEREIN ARE BROUGHTSUCCESSIVELY INTO COMMUNICATION WITH THE PORTS, A PLURALITY OF PISTONSSLIDABLE RESPECTIVELY IN THE PASSAGES AND PROJECTING FROM ONE END OF THEROTOR TOWARDS THE CAM FACE, A PLURALITY OF CUP-SHAPED SLIPPERS MOUNTEDRESPECTIVELY ON THE PISTONS WHERE THESE PROJECT FROM THE ROTOR, EACHSLIPPER INCLUDING A SKIRT PORTION ENCIRCLING THE PISTON, A CUPPED ENDFACE REMOTE FROM THE SKIRT PORTION AND INCLINED TO THE AXIS OF THE SKIRTPORTION AT AN ANGLE EQUAL TO THE INCLINATION OF THE CAM FACE TO THESHAFT AXIS AND A PORTION ENGAGED DIRECTLY AGAINST THE END OF THEASSOCIATED PISTON, AND A PLURALITY OF ELASTOMERIC RINGS COUPLING THERESPECTIVE SLIPPERS TO THE PISTONS, EACH RING BEING SEALINGLY BONDED TOTHE INTERIOR OF THE ASSOCIATED SKIRT PORTION AND TO THE PISTON AND EACHPISTON/SLIPPER COMBINATION HAVING A RESTRICTED BORE CONNECTING THEINTERIOR OF THE ASSOCIATED PASSAGE TO THE INTERIOR OF THE SLIPPER TOFORM BETWEEN EACH SLIPPER AND THE CAM FACE, A HYDROSTATIC BEARING.